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            <h1 style="display: none">js</h1>
            
            
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                <p><img src="/2023/06/12/js/js1.png" srcset="/img/loading.gif" lazyload></p>
<h3 id="一、操作方法"><a href="#一、操作方法" class="headerlink" title="一、操作方法"></a>一、操作方法</h3><h4 id="增"><a href="#增" class="headerlink" title="增"></a>增</h4><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br></pre></td><td class="code"><pre><code class="hljs javascript"><span class="hljs-comment">// 下面前三种是对原数组产生影响的增添方法，第四种则不会对原数组产生影响</span><br><span class="hljs-number">1.</span> <span class="hljs-title function_">push</span>();<br><span class="hljs-number">2.</span> <span class="hljs-title function_">unshift</span>();<br><span class="hljs-number">3.</span> <span class="hljs-title function_">splice</span>();<br><span class="hljs-number">4.</span> <span class="hljs-title function_">concat</span>();<br><br><span class="hljs-title function_">push</span>(); <span class="hljs-comment">//方法接收任意数量的参数，并将它们添加到数组末尾，返回数组的最新长度</span><br><span class="hljs-keyword">let</span> colors = []; <span class="hljs-comment">// 创建一个数组</span><br><span class="hljs-keyword">let</span> count = colors.<span class="hljs-title function_">push</span>(<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>); <span class="hljs-comment">// 推入两项</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(count); <span class="hljs-comment">// 2</span><br><br><br><span class="hljs-title function_">unshift</span>() <span class="hljs-comment">//在数组开头添加任意多个值，然后返回新的数组长度</span><br><span class="hljs-keyword">let</span> colors = <span class="hljs-keyword">new</span> <span class="hljs-title class_">Array</span>(); <span class="hljs-comment">// 创建一个数组</span><br><span class="hljs-keyword">let</span> count = colors.<span class="hljs-title function_">unshift</span>(<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>); <span class="hljs-comment">// 从数组开头推入两项</span><br><span class="hljs-title function_">alert</span>(count); <span class="hljs-comment">// 2</span><br><br><br><span class="hljs-title function_">splice</span>() <span class="hljs-comment">//传入三个参数，分别是开始位置、0（要删除的元素数量）、插入的元素，返回空数组</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>, <span class="hljs-string">&quot;blue&quot;</span>];<br><span class="hljs-keyword">let</span> removed = colors.<span class="hljs-title function_">splice</span>(<span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-string">&quot;yellow&quot;</span>, <span class="hljs-string">&quot;orange&quot;</span>)<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors) <span class="hljs-comment">// red,yellow,orange,green,blue</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(removed) <span class="hljs-comment">// []</span><br><br><br><span class="hljs-title function_">concat</span>() <span class="hljs-comment">//数组合并，将多个数组合并成一个数组，返回新的数组，不会影响原始数组</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>, <span class="hljs-string">&quot;blue&quot;</span>];<br><span class="hljs-keyword">let</span> colors2 = colors.<span class="hljs-title function_">concat</span>(<span class="hljs-string">&quot;yellow&quot;</span>, [<span class="hljs-string">&quot;black&quot;</span>, <span class="hljs-string">&quot;brown&quot;</span>]);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors); <span class="hljs-comment">// [&quot;red&quot;, &quot;green&quot;,&quot;blue&quot;]</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors2); <span class="hljs-comment">// [&quot;red&quot;, &quot;green&quot;, &quot;blue&quot;, &quot;yellow&quot;, &quot;black&quot;, &quot;brown&quot;]</span><br></code></pre></td></tr></table></figure>

<h4 id="删"><a href="#删" class="headerlink" title="删"></a>删</h4><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br></pre></td><td class="code"><pre><code class="hljs javascript"><span class="hljs-comment">// 下面三种都会影响原数组，最后一项不影响原数组：</span><br><span class="hljs-number">1.</span> <span class="hljs-title function_">pop</span>()<br><span class="hljs-number">2.</span> <span class="hljs-title function_">shift</span>()<br><span class="hljs-number">3.</span> <span class="hljs-title function_">splice</span>()<br><span class="hljs-number">4.</span> <span class="hljs-title function_">slice</span>()<br><br><span class="hljs-title function_">pop</span>() <span class="hljs-comment">//方法用于删除数组的最后一项，同时减少数组的 length 值，返回被删除的项</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>]<br><span class="hljs-keyword">let</span> item = colors.<span class="hljs-title function_">pop</span>(); <span class="hljs-comment">// 取得最后一项</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(item) <span class="hljs-comment">// green</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors.<span class="hljs-property">length</span>) <span class="hljs-comment">// 1</span><br><br><br><span class="hljs-title function_">shift</span>() <span class="hljs-comment">//方法用于删除数组的第一项，同时减少数组的 length 值，返回被删除的项</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>]<br><span class="hljs-keyword">let</span> item = colors.<span class="hljs-title function_">shift</span>(); <span class="hljs-comment">// 取得第一项</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(item) <span class="hljs-comment">// red</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors.<span class="hljs-property">length</span>) <span class="hljs-comment">// 1</span><br><br><br><span class="hljs-title function_">splice</span>() <span class="hljs-comment">//传入两个参数，分别是开始位置，删除元素的数量，返回包含删除元素的数组</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>, <span class="hljs-string">&quot;blue&quot;</span>];<br><span class="hljs-keyword">let</span> removed = colors.<span class="hljs-title function_">splice</span>(<span class="hljs-number">0</span>,<span class="hljs-number">1</span>); <span class="hljs-comment">// 删除第一项</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors); <span class="hljs-comment">// green,blue</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(removed); <span class="hljs-comment">// red，只有一个元素的数组</span><br><br><br><span class="hljs-title function_">slice</span>() <span class="hljs-comment">// 用于创建一个包含原有数组中一个或多个元素的新数组，不会影响原始数组</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>, <span class="hljs-string">&quot;blue&quot;</span>, <span class="hljs-string">&quot;yellow&quot;</span>, <span class="hljs-string">&quot;purple&quot;</span>];<br><span class="hljs-keyword">let</span> colors2 = colors.<span class="hljs-title function_">slice</span>(<span class="hljs-number">1</span>);<br><span class="hljs-keyword">let</span> colors3 = colors.<span class="hljs-title function_">slice</span>(<span class="hljs-number">1</span>, <span class="hljs-number">4</span>);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors)   <span class="hljs-comment">// red,green,blue,yellow,purple</span><br>concole.<span class="hljs-title function_">log</span>(colors2); <span class="hljs-comment">// green,blue,yellow,purple</span><br>concole.<span class="hljs-title function_">log</span>(colors3); <span class="hljs-comment">// green,blue,yellow</span><br></code></pre></td></tr></table></figure>

<h4 id="改"><a href="#改" class="headerlink" title="改"></a>改</h4><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br></pre></td><td class="code"><pre><code class="hljs javascript"><span class="hljs-comment">// 即修改原来数组的内容，常用splice</span><br><span class="hljs-number">1.</span> <span class="hljs-title function_">splice</span>()<br><br><span class="hljs-title function_">splice</span>() <span class="hljs-comment">//传入三个参数，分别是开始位置，要删除元素的数量，要插入的任意多个元素，返回删除元素的数组，对原数组产生影响</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>, <span class="hljs-string">&quot;blue&quot;</span>];<br><span class="hljs-keyword">let</span> removed = colors.<span class="hljs-title function_">splice</span>(<span class="hljs-number">1</span>, <span class="hljs-number">1</span>, <span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;purple&quot;</span>); <span class="hljs-comment">// 插入两个值，删除一个元素</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(colors); <span class="hljs-comment">// red,red,purple,blue</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(removed); <span class="hljs-comment">// green，只有一个元素的数组</span><br></code></pre></td></tr></table></figure>

<h4 id="查"><a href="#查" class="headerlink" title="查"></a>查</h4><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br></pre></td><td class="code"><pre><code class="hljs javascript"><span class="hljs-comment">// 即查找元素，返回元素坐标或者元素值</span><br><span class="hljs-number">1.</span> <span class="hljs-title function_">indexOf</span>()<br><span class="hljs-number">2.</span> <span class="hljs-title function_">includes</span>()<br><span class="hljs-number">3.</span> <span class="hljs-title function_">find</span>()<br><br><span class="hljs-title function_">indexOf</span>() <span class="hljs-comment">// 返回要查找的元素在数组中的位置，如果没找到则返回-1</span><br><span class="hljs-keyword">let</span> numbers = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-number">4</span>, <span class="hljs-number">3</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>];<br>numbers.<span class="hljs-title function_">indexOf</span>(<span class="hljs-number">4</span>) <span class="hljs-comment">// 3</span><br><br><br><span class="hljs-title function_">includes</span>() <span class="hljs-comment">//includes 可以判断一个数组中是否包含某一个元素，并返回true 或者false</span><br><span class="hljs-keyword">let</span> arr = [<span class="hljs-string">&quot;a&quot;</span>, <span class="hljs-string">&quot;b&quot;</span>, <span class="hljs-string">&quot;c&quot;</span>];<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(arr.<span class="hljs-title function_">includes</span>(<span class="hljs-string">&quot;a&quot;</span>)); <span class="hljs-comment">// true</span><br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(arr.<span class="hljs-title function_">includes</span>(<span class="hljs-string">&quot;d&quot;</span>)); <span class="hljs-comment">// false</span><br><br><br><span class="hljs-title function_">find</span>() <span class="hljs-comment">//返回第一个匹配的元素</span><br><span class="hljs-keyword">const</span> people = [<br>    &#123;<br>        <span class="hljs-attr">name</span>: <span class="hljs-string">&quot;Matt&quot;</span>,<br>        <span class="hljs-attr">age</span>: <span class="hljs-number">27</span><br>    &#125;,<br>    &#123;<br>        <span class="hljs-attr">name</span>: <span class="hljs-string">&quot;Nicholas&quot;</span>,<br>        <span class="hljs-attr">age</span>: <span class="hljs-number">29</span><br>    &#125;<br>];<br>people.<span class="hljs-title function_">find</span>(<span class="hljs-function">(<span class="hljs-params">element, index, array</span>) =&gt;</span> element.<span class="hljs-property">age</span> &lt; <span class="hljs-number">28</span>) <span class="hljs-comment">// // &#123;name: &quot;Matt&quot;, age: 27&#125;</span><br></code></pre></td></tr></table></figure>

<h3 id="二、排序方法"><a href="#二、排序方法" class="headerlink" title="二、排序方法"></a>二、排序方法</h3><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br></pre></td><td class="code"><pre><code class="hljs javascript"><span class="hljs-comment">// 数组有两个方法可以用来对元素重新排序：</span><br><span class="hljs-number">1.</span> <span class="hljs-title function_">reverse</span>()<br><span class="hljs-number">2.</span> <span class="hljs-title function_">sort</span>()<br><br><span class="hljs-title function_">reverse</span>() <span class="hljs-comment">//顾名思义，将数组元素方向排列</span><br><span class="hljs-keyword">let</span> values = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>];<br>values.<span class="hljs-title function_">reverse</span>();<br><span class="hljs-title function_">alert</span>(values); <span class="hljs-comment">// 5,4,3,2,1</span><br><br><br><span class="hljs-title function_">sort</span>() <span class="hljs-comment">// 方法接受一个比较函数，用于判断哪个值应该排在前面</span><br><span class="hljs-keyword">var</span> arr = [<span class="hljs-number">15</span>,<span class="hljs-number">68</span>,<span class="hljs-number">3</span>,<span class="hljs-number">2</span>,<span class="hljs-number">89</span>];<br>arr.<span class="hljs-title function_">sort</span>(<span class="hljs-function">(<span class="hljs-params">a,b</span>)=&gt;</span>a-b);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(arr)  <span class="hljs-comment">// [2, 3, 15, 68, 89] 升序</span><br><br><br><span class="hljs-keyword">var</span> arr = [<span class="hljs-number">15</span>,<span class="hljs-number">68</span>,<span class="hljs-number">3</span>,<span class="hljs-number">2</span>,<span class="hljs-number">89</span>];<br>arr.<span class="hljs-title function_">sort</span>(<span class="hljs-function">(<span class="hljs-params">a,b</span>)=&gt;</span>b-a);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(arr)  <span class="hljs-comment">// [89, 68, 15, 3, 2] 降序</span><br></code></pre></td></tr></table></figure>

<h3 id="三、转换方法"><a href="#三、转换方法" class="headerlink" title="三、转换方法"></a>三、转换方法</h3><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><code class="hljs javascript"><span class="hljs-number">1.</span> <span class="hljs-title function_">join</span>()<br><br><span class="hljs-title function_">join</span>() <span class="hljs-comment">// 方法接收一个参数，即字符串分隔符，返回包含所有项的字符串</span><br><span class="hljs-keyword">let</span> colors = [<span class="hljs-string">&quot;red&quot;</span>, <span class="hljs-string">&quot;green&quot;</span>, <span class="hljs-string">&quot;blue&quot;</span>];<br><span class="hljs-title function_">alert</span>(colors.<span class="hljs-title function_">join</span>(<span class="hljs-string">&quot;,&quot;</span>)); <span class="hljs-comment">// red,green,blue</span><br><span class="hljs-title function_">alert</span>(colors.<span class="hljs-title function_">join</span>(<span class="hljs-string">&quot;||&quot;</span>)); <span class="hljs-comment">// red||green||blue</span><br></code></pre></td></tr></table></figure>

<h3 id="四、迭代方法"><a href="#四、迭代方法" class="headerlink" title="四、迭代方法"></a>四、迭代方法</h3><figure class="highlight javascript"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br></pre></td><td class="code"><pre><code class="hljs javascript"><span class="hljs-comment">// 常用来迭代数组的方法（都不改变原数组）有如下：</span><br><span class="hljs-number">1.</span> <span class="hljs-title function_">some</span>()<br><span class="hljs-number">2.</span> <span class="hljs-title function_">every</span>()<br><span class="hljs-number">3.</span> <span class="hljs-title function_">forEach</span>()<br><span class="hljs-number">4.</span> <span class="hljs-title function_">filter</span>()<br><span class="hljs-number">5.</span> <span class="hljs-title function_">map</span>()<br><br><span class="hljs-title function_">some</span>() <span class="hljs-comment">// 对数组每一项都运行传入的函数，如果有一项函数返回 true ，则这个方法返回 true</span><br><span class="hljs-keyword">let</span> numbers = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-number">4</span>, <span class="hljs-number">3</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>];<br><span class="hljs-keyword">let</span> someResult = numbers.<span class="hljs-title function_">every</span>(<span class="hljs-function">(<span class="hljs-params">item, index, array</span>) =&gt;</span> item &gt; <span class="hljs-number">2</span>);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(someResult) <span class="hljs-comment">// true</span><br><br><br><span class="hljs-title function_">every</span>() <span class="hljs-comment">// 对数组每一项都运行传入的函数，如果对每一项函数都返回 true ，则这个方法返回 true</span><br><span class="hljs-keyword">let</span> numbers = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-number">4</span>, <span class="hljs-number">3</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>];<br><span class="hljs-keyword">let</span> everyResult = numbers.<span class="hljs-title function_">every</span>(<span class="hljs-function">(<span class="hljs-params">item, index, array</span>) =&gt;</span> item &gt; <span class="hljs-number">2</span>);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(everyResult) <span class="hljs-comment">// false</span><br><br><br><span class="hljs-title function_">forEach</span>() <span class="hljs-comment">//对数组每一项都运行传入的函数，没有返回值</span><br><span class="hljs-keyword">let</span> numbers = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-number">4</span>, <span class="hljs-number">3</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>];<br>numbers.<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">item, index, array</span>) =&gt;</span> &#123;<br>    <span class="hljs-comment">// 执行某些操作</span><br>&#125;);<br><br><br><span class="hljs-title function_">filter</span>() <span class="hljs-comment">//对数组每一项都会遍历，返回为true的元素</span><br><span class="hljs-keyword">let</span> numbers = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-number">4</span>, <span class="hljs-number">3</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>];<br><span class="hljs-keyword">let</span> filterResult = numbers.<span class="hljs-title function_">filter</span>(<span class="hljs-function">(<span class="hljs-params">item, index, array</span>) =&gt;</span> item &gt; <span class="hljs-number">2</span>);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(filterResult); <span class="hljs-comment">// 3,4,5,4,3</span><br><br><br><span class="hljs-title function_">map</span>() <span class="hljs-comment">// 对数组每一项都运行传入的函数，返回由每次函数调用的结果构成的数组</span><br><span class="hljs-keyword">let</span> numbers = [<span class="hljs-number">1</span>, <span class="hljs-number">2</span>, <span class="hljs-number">3</span>, <span class="hljs-number">4</span>, <span class="hljs-number">5</span>, <span class="hljs-number">4</span>, <span class="hljs-number">3</span>, <span class="hljs-number">2</span>, <span class="hljs-number">1</span>];<br><span class="hljs-keyword">let</span> mapResult = numbers.<span class="hljs-title function_">map</span>(<span class="hljs-function">(<span class="hljs-params">item, index, array</span>) =&gt;</span> item * <span class="hljs-number">2</span>);<br><span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(mapResult) <span class="hljs-comment">// 2,4,6,8,10,8,6,4,2</span><br></code></pre></td></tr></table></figure>

                
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      window.anchors.options.class = 'anchorjs-link-left';
    }
    window.anchors.add(res.join(', '));

    Fluid.events.registerRefreshCallback(function() {
      if ('anchors' in window) {
        anchors.removeAll();
        var el = (CONFIG.anchorjs.element || 'h1,h2,h3,h4,h5,h6').split(',');
        var res = [];
        for (var item of el) {
          res.push('.markdown-body > ' + item.trim());
        }
        if (CONFIG.anchorjs.placement === 'left') {
          anchors.options.class = 'anchorjs-link-left';
        }
        anchors.add(res.join(', '));
      }
    });
  });
</script>


  
<script>
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    Fluid.plugins.fancyBox();
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  <script>Fluid.plugins.imageCaption();</script>

  <script  src="/js/local-search.js" ></script>





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<script  src="/js/boot.js" ></script>


  

  <noscript>
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